1. Field of the Invention
The present invention relates to a honeycomb structure, a method of manufacturing the honeycomb structure, a die for forming, and a discharge fluid purification system, particularly to a honeycomb structure preferably usable for exhaust gas purification, water treatment, separating films and the like, a method of manufacturing the honeycomb structure, a die for forming, preferably usable in the manufacturing method, and a discharge fluid purification system in which the honeycomb structure is used.
2. Description of the Related Art
There has been increasingly a need for removing particulates and toxic materials from an exhaust gas of an internal combustion engine, boiler or the like in consideration of an influence on an environment. Especially, regulations on removal of particulate materials (hereinafter referred to as PM) exhausted from diesel engines have tended to be reinforced in Europe, America, and Japan, and a honeycomb filter in which a honeycomb structure is used has been used in a trapping filter (hereinafter referred to as DPF) for removing the PM. The honeycomb filter in which the honeycomb structure is used has also been used in filtration of liquids such as city water and sewage or in the separating films and the like.
When the honeycomb structure is used as the honeycomb filter, for example, as shown in FIGS. 16(a) to (c), the honeycomb structure is used in the form of a honeycomb structure 1 comprising porous partition walls 2 arranged so as to form a plurality of cells 3 extending to an other-end portion 44 from a one-end portion 42 through an axial direction, and plugging portions 4 arranged so as to plug the cells 3 in either end portion. In this form, a fluid to be treated flowing into the cell from the one-end portion 42 is discharged from the other-end portion 44 via another cell 3 through the porous partition wall 2. In this case, the partition wall 2 forms a filter to capture the PM and the like.
However, when the honeycomb structure is used as the DPF or the like, and many deposits such as the PM 9 are deposited on an open end portion of the cell, there are problems that an inflow area of the open end portion decreases or the open end portion is blocked, a pressure loss of the honeycomb filter increases, and an output drop or deterioration of fuel efficiency of the diesel engine is caused.
Moreover, a honeycomb structure which does not have any plugging portion is also used, for example, in removing soluble organic components (hereinafter referred to as SOF) discharged from the diesel engine, but there are problems that the SOF and the like stick to the open end portion, the inflow area of the open end portion decreases, or the open end portion is blocked to increase the pressure loss. Furthermore, this problem of the blocked opening is caused not only in a case where the exhaust gas from the diesel engine is treated but also in a case where gas or liquid is treated as the fluid to be treated.
In a case where the honeycomb structure including the plugging portion is used for the DPF, as a method of preventing a rapid increase of the pressure loss by the deposition of the particulate material, a plugging honeycomb structure has been proposed in which a protruding portion protruding in a shape thinned toward an upstream side from the end portion of the cell is formed in the plugging portion (see Japanese Patent Application Laid-Open No. 2002-309922). However, an appropriate manufacturing method capable of providing the honeycomb structure including the plugging portion shaped in this manner as an industrial product has not been described, and there is not any method capable of industrially manufacturing the structure.
Moreover, a structure whose partition walls are deformed/bent and bonded to each other to close a port of the cell passage in a tip of a square cell passage (see Japanese Patent Application Laid-Open No. 57-7217). Even this structure has an effect of inhibiting the blocking, but it is difficult to form a deformed/bent portion. There has been a demand for a structure in which strength of the deformed/bent portion is further enhanced.